Kristin Cavallari's flawless smile has been featured on TV, film and magazine covers. But the 25-year-old actress and reality-show personality didn't always have a perfect set of teeth. In fact, she told Dear Doctor magazine — where readers recently voted to crown her with the “Smile of the Year” award — that her dental treatments began the same way many do: with orthodontics in sixth grade.

“I had the ‘spaghetti catcher,’ which is what everyone used to call it,” she reminisced. But by that, she didn't mean a strainer — she's talking about what dentists call a “palatal expander.”

In case you're not familiar with this orthodontic device, a palatal expander takes advantage of the natural growth patterns of a child's upper jaw to create additional space for the top set of teeth. How does it work? Basically, it's similar to braces: By applying gentle pressure, the appliance creates changes in the jaw. Unlike braces, however, it's invisible — it fits between the upper teeth, close to the roof of the mouth.

During the three to six months a child wears the palatal expander, it pushes the left and right halves of the upper jawbone apart, and then maintains and stabilizes the new, wider spacing. Since the palatal bones don't fuse until after puberty, tightening it a little bit each day for the first few weeks provides a quick and painless method of making the upper jaw a bit roomier. And that can be a very good thing. Why?

There are lots of reasons. For one, it can relieve the condition called “crowding,” when there is not enough space in the upper jaw to accommodate the proper alignment of the permanent teeth. In the past, teeth often had to be extracted in that situation. It may even allow “impacted” teeth — ones which are blocked from erupting by other teeth — to come in normally.

It can help treat a “crossbite,” when the back top teeth come down to bite inside (instead of outside) the lower back teeth. It also generally shortens the total time a child needs for orthodontic treatment. That's good news for any teenager — even if their own day-to-day “reality show” isn't featured on TV!